Immunoglobulin domain; The members here are composed of the immunoglobulin (Ig) domain found in the Ig superfamily. The Ig superfamily is a heterogenous group of proteins, built on a common fold comprised of a sandwich of two beta sheets. Members of this group are components of immunoglobulin, neuroglia, cell surface glycoproteins, including T-cell receptors, CD2, CD4, CD8, and membrane glycoproteins, including butyrophilin and chondroitin sulfate proteoglycan core protein. A predominant feature of most Ig domains is a disulfide bridge connecting the two beta-sheets with a tryptophan residue packed against the disulfide bond. Ig superfamily (IgSF) domains can be divided into 4 main classes based on their structures and sequences: the Variable (V), Constant 1 (C1), Constant 2 (C2), and Intermediate (I) sets. Typically, the V-set domains have A, B, E, and D strands in one sheet and A', G, F, C, C' and C" in the other. The structures in C1-set are smaller than those in the V-set; they have one beta sheet that is formed by strands A, B, E, and D and the other by strands G, F, C, and C'. Moreover, a C1-set Ig domain contains a short C' strand (three residues) and lacks A' and C" strand. Unlike other Ig domain sets, C2-set structures do not have a D strand. Like the V-set Ig domains, members of the I-set have a discontinuous A strand, but lack a C" strand.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1958797603 223 PYISEAKGTGVPVGQKGTLQCEASAV-PSAEFQWFKDDKRLVEGK-KGVKVENRPFLSRLTFFNVSEHDYGNYTCVASNK 300
Cdd:cd05750     1 PKLKEMKSQTVQEGSKLVLKCEATSEnPSPRYRWFKDGKELNRKRpKNIKIRNKKKNSELQINKAKLEDSGEYTCVVENI 80

                  ....*..
gi 1958797603 301 LGHTNAS 307
Cdd:cd05750    81 LGKDTVT 87

Immunoglobulin domain; The members here are composed of the immunoglobulin (Ig) domain found in the Ig superfamily. The Ig superfamily is a heterogenous group of proteins, built on a common fold comprised of a sandwich of two beta sheets. Members of this group are components of immunoglobulin, neuroglia, cell surface glycoproteins, including T-cell receptors, CD2, CD4, CD8, and membrane glycoproteins, including butyrophilin and chondroitin sulfate proteoglycan core protein. A predominant feature of most Ig domains is a disulfide bridge connecting the two beta-sheets with a tryptophan residue packed against the disulfide bond. Ig superfamily (IgSF) domains can be divided into 4 main classes based on their structures and sequences: the Variable (V), Constant 1 (C1), Constant 2 (C2), and Intermediate (I) sets. Typically, the V-set domains have A, B, E, and D strands in one sheet and A', G, F, C, C' and C" in the other. The structures in C1-set are smaller than those in the V-set; they have one beta sheet that is formed by strands A, B, E, and D and the other by strands G, F, C, and C'. Moreover, a C1-set Ig domain contains a short C' strand (three residues) and lacks A' and C" strand. Unlike other Ig domain sets, C2-set structures do not have a D strand. Like the V-set Ig domains, members of the I-set have a discontinuous A strand, but lack a C" strand.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1958797603  44 NVTVRQGESATLRCTIDNRV-TRVAWLN--RSTILYagNDKWCL-DPRVVLLSNTQTQYSIEIQNVDVYDEGPYTCSVQT 119
Cdd:cd05717     5 DVTVVEGETLTLKCQVSLRDdSSLQWLNpnGQTIYF--NDKRALrDSRYQLLNHSASELSISVSNVTLSDEGVYTCLHYT 82

                          90
                  ....*....|...
gi 1958797603 120 DNhPKTSRVHLIV 132
Cdd:cd05717    83 DP-VSTKKVTVTV 94

Immunoglobulin (Ig)-like domain in neuregulins; The members here are composed of the immunoglobulin (Ig)-like domain in neuregulins (NRGs). NRGs are signaling molecules which participate in cell-cell interactions in the nervous system, breast, heart, and other organ systems, and are implicated in the pathology of diseases including schizophrenia, multiple sclerosis, and breast cancer. There are four members of the neuregulin gene family (NRG-1, NRG-2, NRG-3, and NRG-4). The NRG-1 protein, binds to and activates the tyrosine kinases receptors ErbB3 and ErbB4, initiating signaling cascades. The other NRGs proteins bind one or the other or both of these ErbBs. NRG-1 has multiple functions: in the brain it regulates various processes such as radial glia formation and neuronal migration, dendritic development, and expression of neurotransmitters receptors, while in the peripheral nervous system NRG-1 regulates processes such as target cell differentiation, and Schwann cell survival. There are many NRG-1 isoforms which arise from the alternative splicing of mRNA. Less is known of the functions of the other NRGs. NRG-2 and NRG-3 are expressed predominantly in the nervous system. NRG-2 is expressed by motor neurons and terminal Schwann cells, and is concentrated near synaptic sites and may be a signal that regulates synaptic differentiation. NRG-4 has been shown to direct pancreatic islet cell development towards the delta-cell lineage.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1958797603 223 PYISEAKGTGVPVGQKGTLQCEASAV-PSAEFQWFKDDKRLVEGK-KGVKVENRPFLSRLTFFNVSEHDYGNYTCVASNK 300
Cdd:cd05750     1 PKLKEMKSQTVQEGSKLVLKCEATSEnPSPRYRWFKDGKELNRKRpKNIKIRNKKKNSELQINKAKLEDSGEYTCVVENI 80

                  ....*..
gi 1958797603 301 LGHTNAS 307
Cdd:cd05750    81 LGKDTVT 87

Immunoglobulin domain; This family contains immunoglobulin-like domains.

                          10        20        30        40        50        60        70
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....
gi 1958797603 222 PPYIS-EAKGTGVPVGQKGTLQCEASAVPSAEFQWFKDDKRLVEGKKGVKVENRPFlSRLTFFNVSEHDYGNYTCVASN 299
Cdd:pfam13927   1 KPVITvSPSSVTVREGETVTLTCEATGSPPPTITWYKNGEPISSGSTRSRSLSGSN-STLTISNVTRSDAGTYTCVASN 78

First (N-terminal) immunoglobulin (Ig)-like domain of the nectin-like molecules; member of the V-set of Ig superfamily (IgSF) domains; The members here are composed of the N-terminal immunoglobulin (Ig)-like domain of the nectin-like molecules Necl-1 (also known as cell adhesion molecule 3 (CADM3)), Necl-2 (CADM1), Necl-3 (CADM2), and similar proteins. At least five nectin-like molecules have been identified (Necl-1 to Necl-5). They all have an extracellular region containing three Ig-like domains, a transmembrane region, and a cytoplasmic region. The N-terminal Ig-like domain of the extracellular region belongs to the V-type subfamily of Ig domains, is essential to cell-cell adhesion, and plays a part in the interaction with the envelope glycoprotein D of various viruses. Necl-1, Necl-2, and Necl-3 have Ca(2+)-independent homophilic and heterophilic cell-cell adhesion activity. Necl-1 is specifically expressed in neural tissue, and is important to the formation of synapses, axon bundles, and myelinated axons. Necl-2 is expressed in a wide variety of tissues and is a putative tumour suppressor gene which is downregulated in aggressive neuroblastoma. Necl-3 accumulates in central and peripheral nervous system tissue and has been shown to selectively interact with oligodendrocytes. This group also contains Class-I MHC-restricted T-cell-associated molecule (CRTAM), whose expression pattern is consistent with its expression in Class-I MHC-restricted T-cells.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1958797603  44 NVTVRQGESATLRCTIDNRV-TRVAWLN--RSTILYagNDKWCL-DPRVVLLSNTQTQYSIEIQNVDVYDEGPYTCSVQT 119
Cdd:cd05717     5 DVTVVEGETLTLKCQVSLRDdSSLQWLNpnGQTIYF--NDKRALrDSRYQLLNHSASELSISVSNVTLSDEGVYTCLHYT 82

                          90
                  ....*....|...
gi 1958797603 120 DNhPKTSRVHLIV 132
Cdd:cd05717    83 DP-VSTKKVTVTV 94

Fourth immunoglobulin domain of the Drosophila melanogaster Dscam protein, and similar domains; a member of the I-set of IgSF domains; The members here are composed of the fourth immunoglobulin domain of the Drosophila melanogaster Down syndrome cell adhesion molecule (DSCAM) protein and similar proteins. Down syndrome cell adhesion molecule (DSCAM) is a cell adhesion molecule that plays critical roles in neural development, including axon guidance and branching, axon target recognition, self-avoidance and synaptic formation. DSCAM belongs to the immunoglobulin superfamily and contributes to defects in the central nervous system in Down syndrome patients. Vertebrate DSCAMs differ from Drosophila Dscam1 in that they lack the extensive alternative splicing that occurs in the insect gene. Drosophila melanogaster Dscam has 38,016 isoforms generated by the alternative splicing of four variable exon clusters, which allows every neuron in the fly to display a distinctive set of Dscam proteins on its cell surface. Drosophila Dscam1 is a cell-surface protein that plays important roles in neural development and axon tiling of neurons. It is shown that thousands of isoforms bind themselves through specific homophilic (self-binding) interactions, a process which mediates cellular self-recognition. Drosophila Dscam2 is also alternatively spliced and plays a key role in the development of two visual system neurons, monopolar cells L1 and L2. This group is a member of the I-set Ig domains, having A-B-E-D strands in one beta-sheet and A'-G-F-C-C' in the other. Like the V-set Ig domains, members of the I-set have a discontinuous A strand but lack a C" strand.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1958797603 136 PKIVEISSDISINEGNNISLTCIATGRPEPTVTW----RHISPKA---VG-FVSED----EYLEIQGITREQSGEYECSA 203
Cdd:cd20956     2 PVLLETFSEQTLQPGPSVSLKCVASGNPLPQITWtldgFPIPESPrfrVGdYVTSDgdvvSYVNISSVRVEDGGEYTCTA 81

                  ....*.
gi 1958797603 204 SNDVAA 209
Cdd:cd20956    82 TNDVGS 87

Immunoglobulin V-set domain; This domain is found in antibodies as well as neural protein P0 and CTL4 amongst others.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1958797603  45 VTVRQGESATLRCTI----DNRVTRVAWL-------NRSTILYAGND--KWCLDPRVVLLSNT-QTQYSIEIQNVDVYDE 110
Cdd:pfam07686   6 VTVALGGSVTLPCTYsssmSEASTSVYWYrqppgkgPTFLIAYYSNGseEGVKKGRFSGRGDPsNGDGSLTIQNLTLSDS 85

                          90       100
                  ....*....|....*....|...
gi 1958797603 111 GPYTCSVQTDNHPKTSR-VHLIV 132
Cdd:pfam07686  86 GTYTCAVIPSGEGVFGKgTRLTV 108

Immunoglobulin (Ig)-like domain in neuregulins; The members here are composed of the immunoglobulin (Ig)-like domain in neuregulins (NRGs). NRGs are signaling molecules which participate in cell-cell interactions in the nervous system, breast, heart, and other organ systems, and are implicated in the pathology of diseases including schizophrenia, multiple sclerosis, and breast cancer. There are four members of the neuregulin gene family (NRG-1, NRG-2, NRG-3, and NRG-4). The NRG-1 protein, binds to and activates the tyrosine kinases receptors ErbB3 and ErbB4, initiating signaling cascades. The other NRGs proteins bind one or the other or both of these ErbBs. NRG-1 has multiple functions: in the brain it regulates various processes such as radial glia formation and neuronal migration, dendritic development, and expression of neurotransmitters receptors, while in the peripheral nervous system NRG-1 regulates processes such as target cell differentiation, and Schwann cell survival. There are many NRG-1 isoforms which arise from the alternative splicing of mRNA. Less is known of the functions of the other NRGs. NRG-2 and NRG-3 are expressed predominantly in the nervous system. NRG-2 is expressed by motor neurons and terminal Schwann cells, and is concentrated near synaptic sites and may be a signal that regulates synaptic differentiation. NRG-4 has been shown to direct pancreatic islet cell development towards the delta-cell lineage.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1958797603 223 PYISEAKGTGVPVGQKGTLQCEASAV-PSAEFQWFKDDKRLVEGK-KGVKVENRPFLSRLTFFNVSEHDYGNYTCVASNK 300
Cdd:cd05750     1 PKLKEMKSQTVQEGSKLVLKCEATSEnPSPRYRWFKDGKELNRKRpKNIKIRNKKKNSELQINKAKLEDSGEYTCVVENI 80

                  ....*..
gi 1958797603 301 LGHTNAS 307
Cdd:cd05750    81 LGKDTVT 87

Immunoglobulin domain; This family contains immunoglobulin-like domains.

                          10        20        30        40        50        60        70
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....
gi 1958797603 222 PPYIS-EAKGTGVPVGQKGTLQCEASAVPSAEFQWFKDDKRLVEGKKGVKVENRPFlSRLTFFNVSEHDYGNYTCVASN 299
Cdd:pfam13927   1 KPVITvSPSSVTVREGETVTLTCEATGSPPPTITWYKNGEPISSGSTRSRSLSGSN-STLTISNVTRSDAGTYTCVASN 78

Immunoglobulin domain; Members of the immunoglobulin superfamily are found in hundreds of proteins of different functions. Examples include antibodies, the giant muscle kinase titin and receptor tyrosine kinases. Immunoglobulin-like domains may be involved in protein-protein and protein-ligand interactions.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1958797603 226 SEAKGTGVPVGQKGTLQCEAS-AVPSAEFQWFKDDKRLVEGKKGVKVENRPFLSRLTFFNVSEHDYGNYTCVASNKLGHT 304
Cdd:pfam00047   1 SAPPTVTVLEGDSATLTCSAStGSPGPDVTWSKEGGTLIESLKVKHDNGRTTQSSLLISNVTKEDAGTYTCVVNNPGGSA 80

                  ....
gi 1958797603 305 NASI 308
Cdd:pfam00047  81 TLST 84

First (N-terminal) immunoglobulin (Ig)-like domain of the nectin-like molecules; member of the V-set of Ig superfamily (IgSF) domains; The members here are composed of the N-terminal immunoglobulin (Ig)-like domain of the nectin-like molecules Necl-1 (also known as cell adhesion molecule 3 (CADM3)), Necl-2 (CADM1), Necl-3 (CADM2), and similar proteins. At least five nectin-like molecules have been identified (Necl-1 to Necl-5). They all have an extracellular region containing three Ig-like domains, a transmembrane region, and a cytoplasmic region. The N-terminal Ig-like domain of the extracellular region belongs to the V-type subfamily of Ig domains, is essential to cell-cell adhesion, and plays a part in the interaction with the envelope glycoprotein D of various viruses. Necl-1, Necl-2, and Necl-3 have Ca(2+)-independent homophilic and heterophilic cell-cell adhesion activity. Necl-1 is specifically expressed in neural tissue, and is important to the formation of synapses, axon bundles, and myelinated axons. Necl-2 is expressed in a wide variety of tissues and is a putative tumour suppressor gene which is downregulated in aggressive neuroblastoma. Necl-3 accumulates in central and peripheral nervous system tissue and has been shown to selectively interact with oligodendrocytes. This group also contains Class-I MHC-restricted T-cell-associated molecule (CRTAM), whose expression pattern is consistent with its expression in Class-I MHC-restricted T-cells.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1958797603  44 NVTVRQGESATLRCTIDNRV-TRVAWLN--RSTILYagNDKWCL-DPRVVLLSNTQTQYSIEIQNVDVYDEGPYTCSVQT 119
Cdd:cd05717     5 DVTVVEGETLTLKCQVSLRDdSSLQWLNpnGQTIYF--NDKRALrDSRYQLLNHSASELSISVSNVTLSDEGVYTCLHYT 82

                          90
                  ....*....|...
gi 1958797603 120 DNhPKTSRVHLIV 132
Cdd:cd05717    83 DP-VSTKKVTVTV 94

Immunoglobulin I-set domain;

                          10        20        30        40        50        60        70
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....
gi 1958797603 136 PKIVEISSDISINEGNNISLTCIATGRPEPTVTWRH----ISPKAVGFVSEDEY---LEIQGITREQSGEYECSASNDV 207
Cdd:pfam07679   1 PKFTQKPKDVEVQEGESARFTCTVTGTPDPEVSWFKdgqpLRSSDRFKVTYEGGtytLTISNVQPDDSGKYTCVATNSA 79

Immunoglobulin like; IG domains that cannot be classified into one of IGv1, IGc1, IGc2, IG.

                           10        20        30        40        50        60        70        80
                   ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1958797603  142 SSDISINEGNNISLTCIATGRPEPTVTWRHISPKAVGF--------VSEDEYLEIQGITREQSGEYECSASNDvAAPVVR 213
Cdd:smart00410   1 PPSVTVKEGESVTLSCEASGSPPPEVTWYKQGGKLLAEsgrfsvsrSGSTSTLTISNVTPEDSGTYTCAATNS-SGSASS 79

                   ....*.
gi 1958797603  214 RVKVTV 219
Cdd:smart00410  80 GTTLTV 85

agrin-responsive first immunoglobulin-like domains (Ig1) of the MuSK ectodomain; a member of the I-set of IgSF domains; The members here are composed of the first immunoglobulin-like domains (Ig1) of the Muscle-specific kinase (MuSK). MuSK is a receptor tyrosine kinase specifically expressed in skeletal muscle, where it plays a central role in the formation and maintenance of the neuromuscular junction (NMJ). MuSK is activated by agrin, a neuron-derived heparan sulfate proteoglycan. The activation of MUSK in myotubes regulates the formation of NMJs through the regulation of different processes including the specific expression of genes in subsynaptic nuclei, the reorganization of the actin cytoskeleton and the clustering of the acetylcholine receptors (AChR) in the postsynaptic membrane. The Ig superfamily (IgSF) is a heterogenous group of proteins, built on a common fold comprised of a sandwich of two beta sheets. IgSF domains can be divided into 4 main classes based on their structures and sequences: the Variable (V), Constant 1 (C1), Constant 2 (C2), and Intermediate (I) sets. Unlike the V-set, one of the distinctive features of I-set domains is the lack of a C" strand. The structure of the MuSK lacks this strand and thus it belongs to the I-set of the IgSF. I-set domains are found in several cell adhesion molecules (such as VCAM, ICAM, and MADCAM), and are also present in numerous other diverse protein families, including several tyrosine-protein kinase receptors, the hemolymph protein hemolin, the muscle proteins titin, telokin, and twitchin, the neuronal adhesion molecule axonin-1, and the signaling molecule semaphorin 4D that is involved in axonal guidance, immune function and angiogenesis.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1958797603 142 SSDISINEGNNISLTCIATGRPEPTVTWRH--ISPKA----VGFVSEDEYLEIQGITREQSGEYECSASNDVAAPVVRRV 215
Cdd:cd20970     9 SFTVTAREGENATFMCRAEGSPEPEISWTRngNLIIEfntrYIVRENGTTLTIRNIRRSDMGIYLCIASNGVPGSVEKRI 88

                  ....
gi 1958797603 216 KVTV 219
Cdd:cd20970    89 TLQV 92

Second immunoglobulin (Ig)-like domain of fibroblast growth factor (FGF) receptor_like-1(FGFRL1); member of the I-set of IgSF domains; The members here are composed of the second immunoglobulin (Ig)-like domain of fibroblast growth factor (FGF) receptor like-1(FGFRL1). FGFRL1 is comprised of a signal peptide, three extracellular Ig-like modules, a transmembrane segment, and a short intracellular domain. FGFRL1 is expressed preferentially in skeletal tissues. Similar to FGF receptors, the expressed protein interacts specifically with heparin and with FGF2. FGFRL1 does not have a protein tyrosine kinase domain at its C-terminus; neither does its cytoplasmic domain appear to interact with a signaling partner. It has been suggested that FGFRL1 may not have any direct signaling function, but instead acts as a decoy receptor trapping FGFs and preventing them from binding other receptors.

                          10        20        30        40        50        60        70
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....
gi 1958797603 234 PVGQKGTLQCEASAVPSAEFQWFKDDKRLVEGKKGvkvENRPFLSRLTFFNVSEHDYGNYTCVASNKLGHTNAS 307
Cdd:cd05856    17 PVGSSVRLKCVASGNPRPDITWLKDNKPLTPPEIG---ENKKKKWTLSLKNLKPEDSGKYTCHVSNRAGEINAT 87

First (N-terminal) immunoglobulin (Ig)-like domain of nectin-like molecule-3; member of the V-set of Ig superfamily (IgSF) domains; The members here are composed of the N-terminal immunoglobulin (Ig)-like domain of nectin-like molecule-3, Necl-3 (also known as cell adhesion molecule 2 (CADM2), SynCAM2, IGSF4D). Nectin-like molecules have similar domain structures to those of nectins. At least five nectin-like molecules have been identified (Necl-1 - Necl-5). They all have an extracellular region containing three Ig-like domains, a transmembrane region, and a cytoplasmic region. The N-terminal Ig-like domain of the extracellular region, belongs to the V-type subfamily of Ig domains, is essential to cell-cell adhesion, and plays a part in the interaction with the envelope glycoprotein D of various viruses. Necl-3 accumulates in central and peripheral nervous system tissue, and has been shown to selectively interact with oligodendrocytes.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1958797603  44 NVTVRQGESATLRCTID-NRVTRVAWLNRST-ILYAGNDKWCLDPRVVLLSNTQTQYSIEIQNVDVYDEGPYTCSVQTdn 121
Cdd:cd07701     6 NVTVVEGGTANLTCRVDqNDNTSLQWSNPAQqTLYFDDKKALRDNRIELVRASWHELSISISDVSLSDEGQYTCSLFT-- 83

                          90
                  ....*....|..
gi 1958797603 122 HP-KTSRVHLIV 132
Cdd:cd07701    84 MPvKTSKAYLTV 95

Third immunoglobulin (Ig) domain of contactin; member of the I-set of Ig superfamily (IgSF) domains; The members here are composed of the third immunoglobulin (Ig) domain of contactins. Contactins are neural cell adhesion molecules and are comprised of six Ig domains followed by four fibronectin type III (FnIII) domains anchored to the membrane by glycosylphosphatidylinositol. The first four Ig domains form the intermolecular binding fragment, which arranges as a compact U-shaped module via contacts between Ig domains 1 and 4, and between Ig domains 2 and 3. Contactin-2 (TAG-1, axonin-1) may play a part in the neuronal processes of neurite outgrowth, axon guidance and fasciculation, and neuronal migration. This group also includes contactin-1 and contactin-5. The different contactins show different expression patterns in the central nervous system. During development and in adulthood, contactin-2 is transiently expressed in subsets of central and peripheral neurons. Contactin-5 is expressed specifically in the rat postnatal nervous system, peaking at about 3 weeks postnatal, and a lack of contactin-5 (NB-2) results in an impairment of neuronal activity in the rat auditory system. Contactin-5 is highly expressed in the adult human brain in the occipital lobe and in the amygdala. Contactin-1 is differentially expressed in tumor tissues and may, through a RhoA mechanism, facilitate invasion and metastasis of human lung adenocarcinoma. This group belongs to the I-set of IgSF domains.

                          10        20        30        40        50        60        70
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*
gi 1958797603 136 PKI-VEISSDISINEGNNISLTCIATGRPEPTVTWRHI----SPKAVGFVSEdEYLEIQGITREQSGEYECSASN 205
Cdd:cd04968     1 PSIkVRFPADTYALKGQTVTLECFALGNPVPQIKWRKVdgspSSQWEITTSE-PVLEIPNVQFEDEGTYECEAEN 74

Fourth Ig-like domain from smooth muscle myosin light chain kinase and similar domains ; a member of the I-set of IgSF domains; The members here are composed of the fourth immunoglobulin (Ig)-like domain from smooth muscle myosin light chain kinase (MYLK) and similar domains. The Ig superfamily (IgSF) is a heterogenous group of proteins, built on a common fold comprised of a sandwich of two beta sheets. IgSF domains can be divided into 4 main classes based on their structures and sequences: the Variable (V), Constant 1 (C1), Constant 2 (C2), and Intermediate (I) sets. Unlike the V-set, one of the distinctive features of I-set domains is the lack of a C" strand. The structure of this group shows that the fourth Ig-like domain from myosin light chain kinase lacks this strand and thus belongs to the I-set of the IgSF. I-set domains are found in several cell adhesion molecules (such as VCAM, ICAM, and MADCAM), and are also present in numerous other diverse protein families, including several tyrosine-protein kinase receptors, the hemolymph protein hemolin, the muscle proteins titin, telokin, and twitchin, the neuronal adhesion molecule axonin-1, and the signaling molecule semaphorin 4D that is involved in axonal guidance, immune function and angiogenesis.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1958797603 222 PPYISEAKGTGVPVGQKGTLQCEASAVPSAEFQWFKDDKRLveGKKGVKVENRPFLSRLTFFNVSEHDYGNYTCVASNKL 301
Cdd:cd20976     2 PSFSSVPKDLEAVEGQDFVAQCSARGKPVPRITWIRNAQPL--QYAADRSTCEAGVGELHIQDVLPEDHGTYTCLAKNAA 79

                  ....*....
gi 1958797603 302 GHTNASIML 310
Cdd:cd20976    80 GQVSCSAWV 88

Fourth immunoglobulin (Ig)-like domain of hemolin, and similar domains; a member of the I-set of IgSF domains; The members here are composed of the fourth immunoglobulin (Ig)-like domain of hemolin and similar proteins. Hemolin, an insect immunoglobulin superfamily (IgSF) member containing four Ig-like domains, is a lipopolysaccharide-binding immune protein induced during bacterial infection. Hemolin shares significant sequence similarity with the first four Ig-like domains of the transmembrane cell adhesion molecules (CAMs) of the L1 family. IgSF domains can be divided into 4 main classes based on their structures and sequences: the Variable (V), Constant 1 (C1), Constant 2 (C2), and Intermediate (I) sets. The fourth Ig-like domain of hemolin is a member of the I-set Ig domains, having A-B-E-D strands in one beta-sheet and A'-G-F-C-C' in the other. Like the V-set domains, members of the I-set have a discontinuous A strand but lack a C" strand. I-set domains are found in several cell adhesion molecules (such as VCAM, ICAM, and MADCAM), and are also present in numerous other diverse protein families, including several tyrosine-protein kinase receptors, the muscle proteins titin, telokin, and twitchin, the neuronal adhesion molecule axonin-1, and the signaling molecule semaphorin 4D that is involved in axonal guidance, immune function and angiogenesis.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1958797603 136 PKIV-EISSDISINEGNNISLTCIATGRPEPTVTW----RHISPKAVGFVSEDEYLEIQGITREQSGEYECSASNdVAAP 210
Cdd:cd20978     1 PKFIqKPEKNVVVKGGQDVTLPCQVTGVPQPKITWlhngKPLQGPMERATVEDGTLTIINVQPEDTGYYGCVATN-EIGD 79

                  ....*....
gi 1958797603 211 VVRRVKVTV 219
Cdd:cd20978    80 IYTETLLHV 88

Second immunoglobulin (Ig)-like domain of fibroblast growth factor (FGF) receptor, and similar domains; member of the I-set of IgSF domains; The members here are composed of the second immunoglobulin (Ig)-like domain of fibroblast growth factor (FGF) receptor. FGF receptors bind FGF signaling polypeptides. FGFs participate in multiple processes such as morphogenesis, development, and angiogenesis. FGFs bind to four FGF receptor tyrosine kinases (FGFR1, FGFR2, FGFR3, FGFR4). Receptor diversity is controlled by alternative splicing producing splice variants with different ligand binding characteristics and different expression patterns. FGFRs have an extracellular region comprised of three Ig-like domains, a single transmembrane helix, and an intracellular tyrosine kinase domain. Ligand binding and specificity reside in the Ig-like domains 2 and 3, and the linker region that connects these two. FGFR activation and signaling depend on FGF-induced dimerization, a process involving cell surface heparin or heparin sulfate proteoglycans. This group also contains fibroblast growth factor (FGF) receptor like-1(FGFRL1). FGFRL1 does not have a protein tyrosine kinase domain at its C-terminus; neither does its cytoplasmic domain appear to interact with a signaling partner. It has been suggested that FGFRL1 may not have any direct signaling function, but instead acts as a decoy receptor trapping FGFs and preventing them from binding other receptors.

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                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*..
gi 1958797603 233 VPVGQKGTLQCEASAVPSAEFQWFKDDKRL--VEGKKGVKVENRPFLsrLTFFNVSEHDYGNYTCVASNKLGHTNAS 307
Cdd:cd05729    16 LPAANKVRLECGAGGNPMPNITWLKDGKEFkkEHRIGGTKVEEKGWS--LIIERAIPRDKGKYTCIVENEYGSINHT 90

Third immunoglobulin (Ig)-like domain of Neural Cell Adhesion Molecule 1 (NCAM-1); member of the I-set of IgSF domains; The members here are composed of the third immunoglobulin (Ig)-like domain of Neural Cell Adhesion Molecule (NCAM-1). NCAM plays important roles in the development and regeneration of the central nervous system, in synaptogenesis and neural migration. NCAM mediates cell-cell and cell-substratum recognition and adhesion via homophilic (NCAM-NCAM), and heterophilic (NCAM-non-NCAM), interactions. NCAM is expressed as three major isoforms having different intracellular extensions. The extracellular portion of NCAM has five N-terminal Ig-like domains and two fibronectin type III domains. The double zipper adhesion complex model for NCAM homophilic binding involves Ig1, Ig2, and Ig3. By this model, Ig1 and Ig2 mediate dimerization of NCAM molecules situated on the same cell surface (cis interactions), and Ig3 domains mediate interactions between NCAM molecules expressed on the surface of opposing cells (trans interactions) through binding to the Ig1 and Ig2 domains. The adhesive ability of NCAM is modulated by the addition of polysialic acid chains to the fifth Ig-like domain.

                          10        20        30        40        50        60        70
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*.
gi 1958797603 235 VGQKGTLQCEASAVPSAEFQWFKDDKRLVEGKKgvKVENRPFLSRLTFFNVSEHDYGNYTCVASNKLGHTNASIML 310
Cdd:cd05730    17 LGQSVTLACDADGFPEPTMTWTKDGEPIESGEE--KYSFNEDGSEMTILDVDKLDEAEYTCIAENKAGEQEAEIHL 90

Immunoglobulin domain; This domain contains immunoglobulin-like domains.

                          10        20        30        40        50        60        70
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1958797603 233 VPVGQKGTLQCEASAVPSAEFQWFKDDKRLVEGKkgvkvenrpflsRLTFFNVSEHDYGNYTCVASNKLG 302
Cdd:pfam13895  11 VTEGEPVTLTCSAPGNPPPSYTWYKDGSAISSSP------------NFFTLSVSAEDSGTYTCVARNGRG 68

Third immunoglobulin (Ig)-like domain of the L1 cell adhesion molecule (CAM), and similar domains; The members here are composed of the third immunoglobulin (Ig)-like domain of the L1 cell adhesion molecule (CAM). L1 belongs to the L1 subfamily of cell adhesion molecules (CAMs) and is comprised of an extracellular region having six Ig-like domains and five fibronectin type III domains, a transmembrane region and an intracellular domain. L1 is primarily expressed in the nervous system and is involved in its development and function. L1 is associated with an X-linked recessive disorder, X-linked hydrocephalus, MASA syndrome, and spastic paraplegia type 1, that involves abnormalities of axonal growth. This group also contains the chicken neuron-glia cell adhesion molecule, Ng-CAM and human neurofascin.

                          10        20        30        40        50        60
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*...
gi 1958797603 142 SSDISINEGNNISLTCIATGRPEPTVTWRHIS----PKAVGFVSEDEYLEIQGITREQSGEYECSASN 205
Cdd:cd05731     2 ESSTMVLRGGVLLLECIAEGLPTPDIRWIKLGgelpKGRTKFENFNKTLKIENVSEADSGEYQCTASN 69

First immunoglobulin (Ig)-like constant domain in Robo (roundabout) receptors, and similar domains; The members here are composed of the first immunoglobulin (Ig)-like domain in Roundabout (Robo) receptors. Robo receptors play a role in the development of the central nervous system (CNS), and are receptors of Slit protein. Slit is a repellant secreted by the neural cells in the midline. Slit acts through Robo to prevent most neurons from crossing the midline from either side. Three mammalian Robo homologs (Robo1, Robo2, and Robo3), and three mammalian Slit homologs (Slit1, Slit2, Slit3), have been identified. Commissural axons, which cross the midline, express low levels of Robo; longitudinal axons, which avoid the midline, express high levels of Robo. Robo1, Robo2, and Robo3 are expressed by commissural neurons in the vertebrate spinal cord and Slit1, Slit2,and Slit3 are expressed at the ventral midline. Robo3 is a divergent member of the Robo family which instead of being a positive regulator of Slit responsiveness, antagonizes Slit responsiveness in precrossing axons. The Slit-Robo interaction is mediated by the second leucine-rich repeat (LRR) domain of Slit and the two N-terminal Ig domains of Robo, Ig1 and Ig2. The primary Robo binding site for Slit2 has been shown by surface plasmon resonance experiments and mutational analysis to be is the Ig1 domain, while the Ig2 domain has been proposed to harbor a weak secondary binding site.

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                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1958797603 222 PPYISEAKGTGVPVGQKGTLQCEASAVPSAEFQWFKDDKRLVEGKKgvKVENRPFL---SRLTFFNV-----SEHDYGNY 293
Cdd:cd07693     1 PRIVEHPSDLIVSKGDPATLNCKAEGRPTPTIQWLKNGQPLETDKD--DPRSHRIVlpsGSLFFLRVvhgrkGRSDEGVY 78

                          90
                  ....*....|....*...
gi 1958797603 294 TCVASNKLGHT---NASI 308
Cdd:cd07693    79 VCVAHNSLGEAvsrNASL 96

First (N-terminal) immunoglobulin (Ig)-like domain of nectin-like molecule 2; member of the V-set of Ig superfamily (IgSF) domains; The members here are composed of the N-terminal immunoglobulin (Ig)-like domain of nectin-like molecule-2, Necl-2 (also known as cell adhesion molecule 1 (CADM1), SynCAM1, IGSF4A, Tslc1, sgIGSF, and RA175). Nectin-like molecules have similar domain structures to those of nectins. At least five nectin-like molecules have been identified (Necl-1 - Necl-5). They all have an extracellular region containing three Ig-like domains, a transmembrane region, and a cytoplasmic region. The N-terminal Ig-like domain of the extracellular region, belongs to the V-type subfamily of Ig domains, is essential to cell-cell adhesion, and plays a part in the interaction with the envelope glycoprotein D of various viruses. Necl-2 has Ca(2+)-independent homophilic and heterophilic cell-cell adhesion activity. Necl-2 is expressed in a wide variety of tissues and is a putative tumour suppressor gene, which is downregulated in aggressive neuroblastoma.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1958797603  43 DNVTVRQGESATLRCTIDNRVTRVAWL---NRSTIlYAGNDKWCLDPRVVLLSNTQTQYSIEIQNVDVYDEGPYTCSVQT 119
Cdd:cd05881     4 EDVTVVEGEVATISCRVKNSDDSVIQLlnpNRQTI-YFRDFRPLKDSRFQLVNFSSSELRVSLTNVSISDEGRYFCQLYT 82

                  .
gi 1958797603 120 D 120
Cdd:cd05881    83 D 83

Second Ig-like domain of the giant muscle protein titin Z1z2 in the sarcomeric Z-disk, and similar domains; a member of the I-set of IgSF domains; The members here are composed of the second immunoglobulin (Ig)-like domain of the giant muscle protein titin Z1z2 in the sarcomeric Z-disk and similar proteins. Titin is a key component in the assembly and functioning of vertebrate striated muscles. By providing connections at the level of individual microfilaments, it contributes to the fine balance of forces between the two halves of the sarcomere. The Ig superfamily (IgSF) is a heterogenous group of proteins, built on a common fold comprised of a sandwich of two beta sheets. IgSF domains can be divided into 4 main classes based on their structures and sequences: the Variable (V), Constant 1 (C1), Constant 2 (C2), and Intermediate (I) sets. Unlike the V-set, one of the distinctive features of I-set domains is the lack of a C" strand. The structure of the titin Z1z2 lacks this strand and thus it belongs to the I-set of the IgSF. I-set domains are found in several cell adhesion molecules (such as VCAM, ICAM, and MADCAM), and are also present in numerous other diverse protein families, including several tyrosine-protein kinase receptors, the hemolymph protein hemolin, the muscle proteins titin, telokin, and twitchin, the neuronal adhesion molecule axonin-1, and the signaling molecule semaphorin 4D that is involved in axonal guidance, immune function and angiogenesis.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1958797603 222 PPYISEAKGTGVPVGQKGTLQCEASAVPSAEFQWFKDDKRLvEGKKGVKVENRPFLSRLTFFNVSEHDYGNYTCVASNKL 301
Cdd:cd20972     2 PQFIQKLRSQEVAEGSKVRLECRVTGNPTPVVRWFCEGKEL-QNSPDIQIHQEGDLHSLIIAEAFEEDTGRYSCLATNSV 80

                          90
                  ....*....|
gi 1958797603 302 GHTNASIMLF 311
Cdd:cd20972    81 GSDTTSAEIF 90

Immunoglobulin (Ig)-like domain of the L1 cell adhesion molecule (CAM) and similar proteins; member of the I-set of Ig superfamily (IgSF) domains; The members here are composed of the first immunoglobulin (Ig)-like domain of the L1 cell adhesion molecule (CAM). L1 belongs to the L1 subfamily of cell adhesion molecules (CAMs) and is comprised of an extracellular region having six Ig-like domains and five fibronectin type III domains, a transmembrane region and an intracellular domain. L1 is primarily expressed in the nervous system and is involved in its development and function. L1 is associated with an X-linked recessive disorder, X-linked hydrocephalus, MASA syndrome, or spastic paraplegia type 1, that involves abnormalities of axonal growth. This group also contains NrCAM [Ng(neuronglia)CAM-related cell adhesion molecule], which is primarily expressed in the nervous system, and human neurofascin. This group belongs to the I-set of IgSF domains, having A-B-E-D strands in one beta-sheet and A'-G-F-C-C' in the other. Like the V-set Ig domains, members of the I-set have a discontinuous A strand, but lacks a C" strand.

                          10        20        30        40        50        60
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*
gi 1958797603 240 TLQCEASAVPSAEFQWFKDDKRLVEGKK-GVKVENRPFLSRLTFFNVSEHDY-GNYTCVASNKLG 302
Cdd:cd05733    20 TIKCEAKGNPQPTFRWTKDGKFFDPAKDpRVSMRRRSGTLVIDNHNGGPEDYqGEYQCYASNELG 84

Third immunoglobulin (Ig)-like domain in Robo (roundabout) receptors; member of the I-set of Ig superfamily (IgSF) domains; The members here are composed of the third immunoglobulin (Ig)-like domain in Robo (roundabout) receptors. Robo receptors play a role in the development of the central nervous system (CNS), and are receptors of Slit protein. Slit is a repellant secreted by the neural cells in the midline. Slit acts through Robo to prevent most neurons from crossing the midline from either side. Three mammalian Robo homologs (Robo1, Robo2, Robo3), and three mammalian Slit homologs (Slit-1,Slit-2, Slit-3), have been identified. Commissural axons, which cross the midline, express low levels of Robo; longitudinal axons, which avoid the midline, express high levels of Robo. Robo1, Robo2, and Robo3 are expressed by commissural neurons in the vertebrate spinal cord and Slit-1, Slit-2, and Slit-3 are expressed at the ventral midline. Robo-3 is a divergent member of the Robo family which instead of being a positive regulator of Slit responsiveness, antagonizes Slit responsiveness in precrossing axons. The Slit-Robo interaction is mediated by the second leucine-rich repeat (LRR) domain of Slit and the two N-terminal Ig domains of Robo, Ig1 and Ig2. The primary Robo binding site for Slit2 has been shown by surface plasmon resonance experiments and mutational analysis to be the Ig1 domain, while the Ig2 domain has been proposed to harbor a weak secondary binding site. This group belongs to the I-set of IgSF domains, having A-B-E-D strands in one beta-sheet and A'-G-F-C-C' in the other. Like the V-set Ig domains, members of the I-set have a discontinuous A strand, but lack a C" strand.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1958797603 225 ISEAKGTGVPVGQKGTLQCEASAVPSAEFQWFKDDKRLVEGKKGVKVENRpflsrLTFFNVSEHDYGNYTCVASNKLGHT 304
Cdd:cd05725     1 VKRPQNQVVLVDDSAEFQCEVGGDPVPTVRWRKEDGELPKGRYEILDDHS-----LKIRKVTAGDMGSYTCVAENMVGKI 75

                  ....*.
gi 1958797603 305 NASIML 310
Cdd:cd05725    76 EASATL 81

Fifth Ig-like domain of Roundabout (Robo) homolog 1/2, and similar domains; a member of the I-set of IgSF domains; The members here are composed of the fifth Ig-like domain of Roundabout (Robo) homolog 1/2 and similar domains. Robo receptors play a role in the development of the central nervous system (CNS), and are receptors of Slit protein. Slit is a repellant secreted by the neural cells in the midline. Slit acts through Robo to prevent most neurons from crossing the midline from either side. Three mammalian Robo homologs (Robo1, -2, and -3), and three mammalian Slit homologs (Slit-1,-2, -3), have been identified. Commissural axons, which cross the midline, express low levels of Robo; longitudinal axons, which avoid the midline, express high levels of Robo. Robo1, -2, and -3 are expressed by commissural neurons in the vertebrate spinal cord and Slits 1, -2, -3 are expressed at the ventral midline. Robo-3 is a divergent member of the Robo family which instead of being a positive regulator of slit responsiveness, antagonizes slit responsiveness in precrossing axons. The Slit-Robo interaction is mediated by the second leucine-rich repeat (LRR) domain of Slit and the two N-terminal Ig domains of Robo, Ig1 and Ig2. The primary Robo binding site for Slit2 has been shown by surface plasmon resonance experiments and mutational analysis to be is the Ig1 domain, while the Ig2 domain has been proposed to harbor a weak secondary binding site. The fifth Ig-like domain of Robo 1 and 2 is a member of the I-set Ig domains, having A-B-E-D strands in one beta-sheet and A'-G-F-C-C' in the other. Like the V-set Ig domains, members of the I-set have a discontinuous A strand but lack a C" strand. I-set domains are found in several cell adhesion molecules (such as VCAM, ICAM, and MADCAM), and are also present in numerous other diverse protein families, including several tyrosine-protein kinase receptors

                          10        20        30        40        50        60        70
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*.
gi 1958797603 138 IVEISSDISINEGNNISLTCIATGRPEPTVTWRHispKAVGFVSEDEY--------LEIQGITREQSGEYECSASN 205
Cdd:cd20952     2 ILQGPQNQTVAVGGTVVLNCQATGEPVPTISWLK---DGVPLLGKDERittlengsLQIKGAEKSDTGEYTCVALN 74

Immunoglobulin (Ig)-like I-set domain of Neural Cell Adhesion Molecule 1 (NCAM-1) and similar proteins; The members here are composed of the fourth immunoglobulin (Ig)-like domain of Neural Cell Adhesion Molecule (NCAM-1). NCAM plays important roles in the development and regeneration of the central nervous system, in synaptogenesis and neural migration. NCAM mediates cell-cell and cell-substratum recognition and adhesion via homophilic (NCAM-NCAM), and heterophilic (NCAM-non-NCAM), interactions. NCAM is expressed as three major isoforms having different intracellular extensions. The extracellular portion of NCAM has five N-terminal Ig-like domains and two fibronectin type III domains. The double zipper adhesion complex model for NCAM homophilic binding involves Ig1, Ig2, and Ig3. By this model, Ig1 and Ig2 mediate dimerization of NCAM molecules situated on the same cell surface (cis interactions), and Ig3 domains mediate interactions between NCAM molecules expressed on the surface of opposing cells (trans interactions), through binding to the Ig1 and Ig2 domains. The adhesive ability of NCAM is modulated by the addition of polysialic acid chains to the fifth Ig-like domain. Also included in this group is NCAM-2 (also known as OCAM/mamFas II and RNCAM) NCAM-2 is differentially expressed in the developing and mature olfactory epithelium (OE). One of the unique features of I-set domains is the lack of a C" strand. The structures of this group show that the Ig domain lacks this strand and thus is a member of the I-set of Ig domains.

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                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1958797603 134 VSPKIVEISSDISInEGNNISLTCIATGRPEPTVTWRHISPkavGFVSE----DEYLEIQGITREQS-----------GE 198
Cdd:cd05732     1 VQPKITYLENQTAV-ELEQITLTCEAEGDPIPEITWRRATR---GISFEegdlDGRIVVRGHARVSSltlkdvqltdaGR 76

                  ....*..
gi 1958797603 199 YECSASN 205
Cdd:cd05732    77 YDCEASN 83

Fifth immunoglobulin (Ig)-like domain of the carcinoembryonic antigen (CEA) related cell adhesion molecule 5 (CEACAM5) and similar domains; member of the C2-set IgSF domains; The members here are composed of the fifth immunoglobulin (Ig)-like domain of the carcinoembryonic antigen (CEA) related cell adhesion molecule 5 (CEACAM5) and similar domains. The CEA family is a group of anchored or secreted glycoproteins, expressed by epithelial cells, leukocytes, endothelial cells and placenta. The CEA family is divided into the CEACAM and pregnancy-specific glycoprotein (PSG) subfamilies. Carcinoembryonic antigen-related cell adhesion molecule 5 (CEACAM5), also known as CD66e (Cluster of Differentiation 66e), is a cell surface glycoprotein that plays a role in cell adhesion, intracellular signaling and tumor progression. Diseases associated with CEACAM5 include lung cancer and rectum cancer. IgSF domains can be divided into 4 main classes based on their structures and sequences: the Variable (V), Constant 1 (C1), Constant 2 (C2), and Intermediate (I) sets. This group belongs to the C2-set of IgSF domains, having A, B, and E strands in one beta-sheet and A', G, F, C' in the other. Unlike other Ig domain sets, the C2-set lacks the D strand.

                          10        20        30        40        50        60        70
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*...
gi 1958797603 142 SSDISINEGNNISLTCIATGRPEPTVTWRhISPKavgFVSEDEYLEIQGITREQSGEYECSASNDVAAPVVRRVKVTV 219
Cdd:cd20948     2 PSDTYYLSGENLNLSCHAASNPPAQYSWT-INGT---FQTSSQELFLPAITENNEGTYTCSAHNSLTGKNISLVLSVT 75

Immunoglobulin (Ig)-like domain of the human basement membrane heparan sulfate proteoglycan perlecan and similar proteins; The members here are composed of the immunoglobulin (Ig)-like domain of the human basement membrane heparan sulfate proteoglycan perlecan, also known as HSPG2, and similar proteins. Perlecan consists of five domains: domain I has three putative heparan sulfate attachment sites, domain II has four LDL receptor-like repeats, and one Ig-like repeat, domain III resembles the short arm of laminin chains, domain IV has multiple Ig-like repeats (21 repeats in human perlecan), and domain V resembles the globular G domain of the laminin A chain and internal repeats of EGF. Perlecan may participate in a variety of biological functions including cell binding, LDL-metabolism, basement membrane assembly and selective permeability, calcium binding, and growth- and neurite-promoting activities.

                          10        20        30        40        50        60
                  ....*....|....*....|....*....|....*....|....*....|....*....|...
gi 1958797603 150 GNNISLTCIATGRPEPTVTWR----HI-SPKAVGFVSEDEY--LEIQGITREQSGEYECSASN 205
Cdd:cd05743     1 GETVEFTCVATGVPTPIINWRlnwgHVpDSARVSITSEGGYgtLTIRDVKESDQGAYTCEAIN 63

Immunoglobulin domain; Members of the immunoglobulin superfamily are found in hundreds of proteins of different functions. Examples include antibodies, the giant muscle kinase titin and receptor tyrosine kinases. Immunoglobulin-like domains may be involved in protein-protein and protein-ligand interactions.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1958797603  44 NVTVRQGESATLRCTIDNRVTRVA---WLNRSTILyagndkwcLDPRVVLLSNTQTQYSIEIQNVDVYDEGPYTCSVQTD 120
Cdd:pfam00047   5 TVTVLEGDSATLTCSASTGSPGPDvtwSKEGGTLI--------ESLKVKHDNGRTTQSSLLISNVTKEDAGTYTCVVNNP 76

                  ....*...
gi 1958797603 121 NHPKTSRV 128
Cdd:pfam00047  77 GGSATLST 84

First immunoglobulin (Ig)-like constant domain in Robo (roundabout) receptors, and similar domains; The members here are composed of the first immunoglobulin (Ig)-like domain in Roundabout (Robo) receptors. Robo receptors play a role in the development of the central nervous system (CNS), and are receptors of Slit protein. Slit is a repellant secreted by the neural cells in the midline. Slit acts through Robo to prevent most neurons from crossing the midline from either side. Three mammalian Robo homologs (Robo1, Robo2, and Robo3), and three mammalian Slit homologs (Slit1, Slit2, Slit3), have been identified. Commissural axons, which cross the midline, express low levels of Robo; longitudinal axons, which avoid the midline, express high levels of Robo. Robo1, Robo2, and Robo3 are expressed by commissural neurons in the vertebrate spinal cord and Slit1, Slit2,and Slit3 are expressed at the ventral midline. Robo3 is a divergent member of the Robo family which instead of being a positive regulator of Slit responsiveness, antagonizes Slit responsiveness in precrossing axons. The Slit-Robo interaction is mediated by the second leucine-rich repeat (LRR) domain of Slit and the two N-terminal Ig domains of Robo, Ig1 and Ig2. The primary Robo binding site for Slit2 has been shown by surface plasmon resonance experiments and mutational analysis to be is the Ig1 domain, while the Ig2 domain has been proposed to harbor a weak secondary binding site.